Disclosed herein is an ink composition comprising at least one curable monomer; at least one gellant; an optional photoinitiator; and an optional colorant; wherein the ink composition has a viscosity of less than 106 centipoise at a temperature of from about 20° C. to about 40° C.; and wherein the ink composition has the characteristics of being both ink jettable and pinnable at a temperature of from about 20° C. to about 40° C.
Also disclosed is a method for printing comprising disposing an ink composition in an imagewise pattern onto an intermediate transfer member or directly onto a final image receiving substrate; optionally, when an intermediate transfer member is used, transferring the ink in the imagewise pattern from the intermediate transfer member to a final recording substrate; exposing the imagewise pattern to radiation to cure the ink; wherein the ink composition comprises at least one curable monomer; at least one gellant; an optional photoinitiator; and an optional colorant; wherein the ink composition has a viscosity of less than 106 centipoise at a temperature of from about 20° C. to about 40° C.; and wherein the ink composition has the characteristics of being both ink jettable and pinnable at a temperature of from about 20° C. to about 40° C.
In general, phase change inks (sometimes referred to as “hot melt inks”) are in the solid phase at ambient temperature, but exist in the liquid phase at the elevated operating temperature of an ink jet printing device. At the jet operating temperature, droplets of liquid ink are ejected from the printing device and, when the ink droplets contact the surface of the recording substrate, either directly or via an intermediate heated transfer belt or drum, they quickly solidify to form a predetermined pattern of solidified ink drops. Phase change inks have also been used in other printing technologies, such as gravure printing.
Phase change inks for color printing typically comprise a phase change ink carrier composition which is combined with a phase change ink compatible colorant. A series of colored phase change inks can be formed by combining ink carrier compositions with compatible subtractive primary colorants. The subtractive primary colored phase change inks can comprise four component dyes, namely, cyan, magenta, yellow and black, although the inks are not limited to these four colors. These subtractive primary colored inks can be formed by using a single dye or a mixture of dyes. For example, magenta can be obtained by using a mixture of Solvent Red Dyes or a composite black can be obtained by mixing several dyes. U.S. Pat. Nos. 4,889,560, 4,889,761, and 5,372,852, the disclosures of each of which are totally incorporated herein by reference, teach that the subtractive primary colorants employed can comprise dyes from the classes of Color Index (C.I.) Solvent Dyes, Disperse Dyes, modified Acid and Direct Dyes, and Basic Dyes. The colorants can also include pigments, as disclosed in, for example, U.S. Pat. No. 5,221,335, the disclosure of which is totally incorporated herein by reference. U.S. Pat. No. 5,621,022, the disclosure of which is totally incorporated herein by reference, discloses the use of a specific class of polymeric dyes in phase change ink compositions.
Phase change inks have also been used for applications such as postal marking, industrial marking, and labeling.
Phase change inks are desirable for ink jet printers because they remain in a solid phase at room temperature during shipping, long term storage, and the like. In addition, the problems associated with nozzle clogging as a result of ink evaporation with liquid ink jet inks are largely eliminated, thereby improving the reliability of the ink jet printing. Further, in phase change ink jet printers wherein the ink droplets are applied directly onto the final recording substrate (for example, paper, transparency material, and the like), the droplets solidify immediately upon contact with the substrate, so that migration of ink along the printing medium is prevented and dot quality is improved.
Compositions suitable for use as phase change ink carrier compositions are known. Suitable carrier materials can include paraffins, microcrystalline waxes, polyethylene waxes, ester waxes, fatty acids and other waxy materials, fatty amide containing materials, sulfonamide materials, resinous materials made from different natural sources (tall oil rosins and rosin esters, for example), and many synthetic resins, oligomers, polymers, and copolymers.
Current ultraviolet curable gellant inks are liquid at elevated temperatures, typically having viscosities of from about 10 to about 15 centipoise at jetting temperatures, with jetting temperatures typically being from about 80° C. about 120° C., and having a viscosity of greater than 104 centipoise at room temperature (about 25° C.) which pins the ink drops in place, sometimes without the need for intermediate cure. After printing, the printed markings are cured to provide robust images.
U.S. Pat. No. 7,501,015, which is hereby incorporated by reference herein in its entirety, describes in the Abstract thereof a phase change ink that has a viscosity of from about 4 mPa-s to about 50 mPa-s at a first temperature and has a viscosity of from 104 mPa-s to about 109 mPa-s at a second lower temperature. The second temperature may be below the first temperature by at least 10° C., but by no more than 50° C. The first temperature may be from about 60° C. to about 110° C. and the second temperature may be from about 20° C. to about 70° C. A curve of log10 viscosity of the phase change ink plotted against temperature in degrees Celsius may have a slope having an absolute value less than 0.02 at the first temperature and have a slope having an absolute value greater than 0.08 for at least a region second temperature.
U.S. Pat. No. 8,507,584, which is hereby incorporated by reference herein in its entirety, describes in the Abstract thereof a phase change ink comprising a colorant, an initiator, and a phase change ink carrier, said carrier comprising at least one radically curable monomer compound and a compound of the formula

wherein R1 and R1′ are the same, and wherein R1 and R1′ are each an aromatic group; and wherein R2 and R2′ and R3 each, independently of the others, are alkylene groups, arylene groups, arylalkylene groups, or alkylarylene groups; or wherein, in embodiments, R1 and R1′ can be the same or different, and wherein R1 and R1′ each, independently of the other is an alkyl group having a least one ethylenic unsaturation, an arylalkyl group having at least one ethylenic unsaturation, an alkylaryl group having at least one ethylenic unsaturation, or an aromatic group, provided that at least one of R1 and R1′ is an aromatic group; and provided that neither of R1 or R1′ is a photoinitiator group. Also disclosed herein is a method of printing with the phase change ink.
U.S. Pat. No. 8,882,256, which is hereby incorporated by reference herein in its entirety, describes in the Abstract thereof curable solid inks which are solid at room temperature and molten at an elevated temperature at which the molten ink is applied to a substrate. In particular, the curable solid inks comprise low molecular weight amide gellants that impart self-leveling capabilities to the inks. Also disclosed herein are methods for making the amide gellant and the inks comprising the amide gellants.
U.S. Pat. No. 8,940,935, which is hereby incorporated by reference herein in its entirety, describes in the Abstract thereof curable inks including a bis-urea gelator having the structure of Formula I

wherein R and R′ each, independently of the other, is a saturated aliphatic hydrocarbon group selected from the group consisting of (1) linear aliphatic groups, (2) branched aliphatic groups, (3) cyclic aliphatic groups, (4) aliphatic groups containing both cyclic and acyclic portions, any carbon atom of the saturated aliphatic hydrocarbon groups may be optionally substituted with an alkyl group (cyclic or acyclic), wherein (1) and (2) groups have a carbon number of from about 1 to about 22 carbons, and wherein (3) and (4) groups have a carbon number of from about 4 to about 10 carbons; and X is selected from the groups consisting of: (i) an alkylene groups, (ii) an arylene group, (iii) an arylalkylene group, and (iv) an alkylarylene group.
While known compositions and processes may be suitable for their intended purposes, a need remains for improved phase change ink compositions. Further, a need remains for improved curable gellant ink compositions. Still further, a need remains for improved curable gellant ink compositions that can be jetted at reduced temperatures. Still further, a need remains for improved curable gellant ink compositions that retain the broad substrate latitude afforded by current compositions. Still further, a need remains for improved curable gellant ink compositions that can be jetted at reduced temperatures without the need for immediate curing after printing or jetting. Still further, a need remains for improved curable gellant ink compositions that are easy to spread or level.
The appropriate components and process aspects of the each of the foregoing U.S. Patents and Patent Publications may be selected for the present disclosure in embodiments thereof. Further, throughout this application, various publications, patents, and published patent applications are referred to by an identifying citation. The disclosures of the publications, patents, and published patent applications referenced in this application are hereby incorporated by reference into the present disclosure to more fully describe the state of the art to which this invention pertains.